Why is an unconventional hydrocarbon reservoir unconventional? An investigation into petrophysical and fluid composition controls.

为什么非常规油气藏是非常规的？

• 批准号: RGPIN-2018-05695
• 负责人: Harris, Nicholas
• 金额: $ 3.64万
• 依托单位: University of Alberta
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=750898
• 关键词: Why; unconventional; hydrocarbon; reservoir; investigation

Unconventional petroleum reservoirs represent the largest fraction of remaining hydrocarbon reservoirs in the world. The most striking feature of these reservoirs, in addition to low permeability, is the unusual, unpredictable nature of fluid distributions: the lack of an obvious top seal and less dense (more buoyant) fluids underlying more dense fluids. Thus, gas or oil can accumulate in low permeability formations that underlie high permeability formations, and gas pools may underlie water or oil columns. Petrophysical properties and capillary forces clearly underpin the unusual distribution of fluids in unconventional petroleum accumulations, which are not found in high permeability formations. In multiphase systems, buoyant forces are balanced against surface tension at the fluid interfaces and the wettability of fluids on solid materials. Thus, shales seal hydrocarbons below a sandstone-shale contact, even though the overlying shale maybe water-saturated. If this applies to unconventional reservoirs, some combination of rock fabric (composition plus texture) interacts with fluid properties (buoyancy, composition, surface tension) to produce unusual segregations of fluids. But how fluid and petrophysical properties control fluid distributions is not understood.Four reservoir units provide natural laboratories for testing models that describe unconventional reservoirs: (1) the hydrocarbon-rich Montney Formation in western Canada that contains conventional hydrocarbon accumulations where it is shallow (distinct top seal, gas over oil over water) but unconventional accumulations where it is deep (no distinct top seal, variable and unsystematic fluid distributions); (2) the Upper Cretaceous large tight-gas-sand accumulations in the U.S. Rocky Mountains where lower permeability reservoirs underlie high permeability caprocks; (3) Lower Cretaceous tight oil/gas sandstones in Alberta with complex pore systems that require hydraulic stimulation to produce; and (4) Duvernay Formation, a shale liquids reservoir where rocks are variably oil-wet, water-wet and have mixed wettability in different parts of the reservoir.I will combine field data and quantitative modeling to develop models for fluid distributions in unconventional reservoirs and to identify tipping points that distinguish conventional from unconventional accumulations. Computationally powerful software can simulate migration of hydrocarbon fluids under the influence of both capillary and buoyancy forces. Such software has not previously been applied to unconventional petroleum systems and may require additional development. This analysis will, in the end, yield new, more precise models for hydrocarbon migration, trapping and distribution in unconventional petroleum systems, tested on important petroleum systems in Canada and the United States and globally applicable.

非常规油气藏在世界剩余油气藏中所占比例最大。除了低渗透率外，这些油藏最显著的特征是流体分布的不同寻常、不可预测的性质：缺乏明显的顶部封闭，以及密度较高的流体下面的密度较低(浮力较大)的流体。因此，天然气或石油可以聚集在高渗透率地层下面的低渗透率地层中，而气藏可能在水柱或油柱下面。岩石物理性质和毛细管力清楚地支持了非常规石油藏中流体的异常分布，这在高渗透率地层中是找不到的。在多相体系中，浮力与流体界面的表面张力和流体在固体材料上的润湿性相平衡。因此，页岩封闭了砂岩-页岩接触面下的碳氢化合物，即使上面的页岩可能是水饱和的。如果这适用于非常规储层，岩石组构(成分和结构)的某种组合与流体属性(浮力、成分、表面张力)相互作用，产生不寻常的流体分离。但流体和岩石物理性质如何控制流体分布还不清楚。四个储集层单元为描述非常规油藏的模型测试提供了天然实验室：(1)加拿大西部富含碳氢化合物的Montney组，它包含常规油气藏，其浅处(明显的顶盖，油上油)，但在它深的地方(没有明显的顶封，可变的和不系统的流体分布)；(2)美国落基山脉的上白垩统大型致密砂岩储集层，低渗透率储集层位于高渗透率盖层之下；(3)阿尔伯塔省下白垩统致密油气砂岩，具有复杂的孔隙系统，需要水力刺激才能生产；(4)杜维奈组，页岩液体储层，岩石具有可变的油湿、水湿，并在储层的不同部分具有混合润湿性。我将结合现场数据和定量模拟来建立非常规储层中流体分布的模型，并识别区分常规和非常规聚集的转折点。计算功能强大的软件可以模拟毛细管力和浮力共同作用下的油气流体运移。这类软件以前没有被应用于非常规石油系统，可能需要进一步开发。这种分析最终将产生新的、更精确的非常规石油系统中的碳氢化合物运移、圈闭和分布模型，并在加拿大和美国的重要石油系统上进行测试，并在全球适用。